A multicarrier communication system such as, e.g., Orthogonal Frequency Division Multiplexing (OFDM), Discrete Multi-tone (DMT) and the like, is typically characterized by a frequency band associated with a communication channel being divided into a number of smaller sub-bands (subcarriers herein). Communication of information (e.g., data, audio, video, etc.) between stations in a multicarrier communication system is performed by dividing the informational content into multiple pieces (e.g., symbols), and then transmitting the pieces in parallel via a number of the separate subcarriers. When the symbol period transmitted through a subcarrier is longer than a maximum multipath delay in the channel, the effect of intersymbol interference between the subcarriers may be significantly reduced.
By simultaneously transmitting content through a number of subcarriers within the channel, multicarrier communication systems offer much promise for high-throughput wireless applications such as, e.g., wireless personal area network, local area network, metropolitan area network, fixed broadband wireless access, and the like. Each of these networking environments present their own challenges and, as such, a system designed to operate in one environment may not be suitable for other environments.
In broadband wireless access (BWA) networks (e.g., those described in the IEEE 802.16a standard, referred to below), deep fades may occur that can persist over a significant period of time. Further, such wide-area wireless channels encounter significant dispersion due to multipath propagation that limits the maximum achievable rates. Since BWA is intended to compete with cable modems and xDSL where the channel is static and non-fading, such system designs must counteract these key challenges and provide high data-rate access at almost wireline quality. To date, conventional techniques such as space-time block encoding, etc. fail to sustain the coding rate while providing the diversity gain as the number of transmit antenna increase past two (2). In this regard, such conventional techniques for providing broadband wireless access typically have to trade data rate (or, throughput) for received channel quality.